This invention relates to a composite sheet having an elastic stretchability in one direction and more particularly to such a composite sheet suitable for topsheet materials for sanitary articles such as diapers, menstruation pads and the like.
Japanese Patent Application Publication No. 1995-328061A describes a topsheet comprising a liquid-pervious nonwoven fabric and a plurality of fine thermoplastic film strips extending in one direction and being spaced apart one from another transversely of the one direction and integrally bonded to the upper surface of the nonwoven fabric.
In the topsheet disclosed by the Publication, both the nonwoven fabric and the plastic film strips have no rubber-based elasticity and the topsheet does not have any elastic stretchability unless the topsheet is subjected to a special treatment. To ensure that this topsheet has an elastic stretchability, an elastically stretchable nonwoven fabric made of fibers obtained by melting and spinning thermoplastic elastomer should be used as the nonwoven fabric and elastically stretchable film obtained by extrusion molding thermoplastic elastomer should be used as the plastic film.
However, both a rubber-based elastically stretchable nonwoven fabric and a rubber-based elastically stretchable film inevitably have an uncomfortable touch such as a sticky or slimy touch and a body fluid absorbent sanitary article such as a disposable diaper or a sanitary napkin using the elastically stretchable nonwoven fabric and the elastically stretchable film may give a wearer of such article uncomfortable feeling if these materials come in contact with the wearer""s skin.
It is an object of this invention to provide a composite sheet having an elastic stretchability and being free from a sticky or slimy touch without using any rubber-based material such as thermoplastic elastomer.
According to this invention, there is provided a composite sheet comprising a nonwoven fabric and a plurality of fine, flexible and continuous filaments extending parallel one to another in a first direction and spaced apart one from another transversely of the first direction.
The composite sheet further comprises an embodiment in which the nonwoven fabric and the continuous filaments are formed with a plurality of recoverable crepes extending in a second direction orthogonal to the first direction and continuously arranged in the first direction so that the nonwoven fabric and the continuous filaments may contract in the first direction at a predetermined ratio with respect to unit length of the composite sheet as measured in the first direction prior to formation of crepes in the nonwoven fabric and the continuous filaments and thereby the composite sheet has an elastic stretchability in the first direction.
The composite sheet according to this invention has an elastic stretchability in the first direction in spite of the fact that the composite sheet comprises the nonwoven fabric made from non-elastomeric thermoplastic synthetic resin fiber and the flexible continuous filaments made from non-elastomeric thermoplastic synthetic resin and bonded to the nonwoven fabric. This is achieved by the feature of this invention such that the nonwoven fabric and the filaments are formed with a plurality of crepes extending in the first direction and continuously arranged a second direction orthogonal to the first direction. The nonwoven fabric and the filaments both having no rubber-based elasticity can be stretched under tension substantially lower than that required to stretch the composite sheet comprising a rubber-based nonwoven fabric and filament.
The composite sheet using none of rubber-based materials such as thermoplastic elastomer is free from a sticky or slimy touch and it is not apprehended that the composite sheet might give a wearer of body fluid absorbent sanitary article using this composite sheet uncomfortable feeling even if the composite sheet comes in contact with the wearer""s skin. The composite sheet according to this invention enables its strength as well as its shape- and dimension-stability to be improved by bonding a plurality of filaments to the nonwoven fabric. Accordingly, the composite sheet will be suitable, for example, for topsheet materials for sanitary articles such as diapers, menstruation pads, panty liners, incontinence pads and the like.